Many applications can benefit from inclusion of a display. For example, sketching apparatuses, telephones, pocketbooks, and battery indicators are only a few applications that could display transient information. To date, widespread incorporation of displays has been hindered because such applications generally require flexible displays that consume very little power.
Despite much effort directed to developing highly-flexible, reflective display media, there are relatively few examples of displays formed on semi-flexible substrates, and these examples have found only moderate success. For example, plastic-based liquid crystal displays, including twisted nematic (TN), supertwisted nematic (STN), polymer dispersed liquid crystal (PDLC), and bistable cholesteric liquid crystals have been developed. Nevertheless, problems remain with liquid crystal alignment in TN and STN displays, cholesteric displays are sensitive to changes in their cell gap, and local stress can cause changes in the scattering or absorbance of PDLC and cholesteric films. As such, only moderate flexibility can be achieved with these displays.
Emissive electroluminescent films and organic light emitting diode films can be deposited on flexible substrates to create flexible displays. However, these devices require continuous power consumption for operation, and thus are not practical for many applications.
Another problem with developing highly flexible displays is the lack of an appropriate conductor for addressing the display elements. Typically, an indium tin oxide (ITO) layer vacuum sputtered onto a plastic substrate is used as a top conductor for displays. An ITO layer, however, can be damaged when the display is flexed. If the local curvature of the plastic substrate becomes too great, the ITO layer tends to crack, damaging the display.